This invention relates to hydraulic force multipling devices.
Various hydraulic force multiplying devices have been proposed to reliably actuate a braking system of a vehicle with a relatively small input force by utilizing hydraulic pressure to multiply the input force thereby generating a large output force.
One of the prior art hydraulic force multiplying devices includes a main body having an inlet port connected to a source of hydraulic pressure and an outlet port connected to means such as a reservoir of hydraulic fluid, an input rod and an output rod with the respective one ends thereof being disposed in the main body and connected slidably with one another, an annular piston slidably engaging with the inner circumference of the main body and with the outer circumference of the input rod, an inlet side liquid chamber and an outlet side liquid chamber defined in the main body and partitioned by the piston, a connecting passage formed in the input rod for connecting the two liquid chambers, and a valve mechanism provided between the input and output rods. The valve mechanism restricts the fluid flow passing through the connecting passage when an input force is applied to the input rod to displace the input rod toward the output rod thereby generating a differential pressure across the piston. The differential pressure force acting on the piston is transmitted to the output rod.
However, there is a shortcoming in the hydraulic force multiplying device having the construction as described heretofore in that the differential pressure will not be established very early across the piston in the initial stage of the actuation of the device so that there is a delay between the application of the input force and the generation of the output force and thus the operator will feel uneasy. Further, when the valve mechanism consists of a rigid valve seat formed on either the input or the output rod and a rigid valve member provided on the other of the input and ouptut rods, the valve member will sometimes engage with the valve seat with an impact thus generating noise and impairing the operational feeling of the device.